The site of Castelgrande has been fortified since at least the late 1st century BC and until the 13th century it was the only fortification in Bellinzona. During its history the castle has been known as the stronghold (before the 13th century), the Old Castle in the 14–15th centuries, Un Castle after 1506 and Saint Michael's Castle from 1818.
The Castelgrande hill includes a nearly vertical side on the north and a steep southern side, but is nearly flat and 150–200 meters in diameter. The natural shape of the hill has encouraged every man-made fortification to follow the same contours. While the Roman fort is not visible the Roman foundations were used by the High Middle Ages castle which followed. Of the High Middle Ages castle the only visible parts are a few pieces of wall that are still standing. Much of the visible castle dates from 1250–1500 with extensive renovations and some expansion in the last two centuries. Most of the area inside the castle walls is now flat, open space.
Records from the 11th to 15th centuries as well as archeological evidence indicate that the castle grounds were once full of buildings. However most of these were pulled down by the Dukes of Milan to free up interior space. The open space was divided into 3 large baileys which served to provide temporary housing for troops that could be stationed in Bellinzona. Under the Dukes of Milan the outer fortifications were extended and strengthened. The walls were raised, extended and towers were added. The western walls were totally rebuilt and connected to the city walls.
The walls that separate the three baileys all radiate from the 14th century Terre Nera, which is located in the center of the castle. To the east is a complex of buildings which were part of the old keep in the castle. In the center of the keep is the tallest tower of Castelgrande, the Torre Bianca or White Tower, which dates from the 13th century. Surrounding the Torre Bianca is the palace of the Bishop of Como (mentioned in the 12th century), which may contain masonry from an earlier 10th or 11th century structure. The nearby South Wing, which marks the southern boundary of the castle, was built in two stages during the 13th and 15th centuries on the foundations of an earlier building. To the west of the South Wing is a building that was built as an arsenal during the 19th century, and was fully renovated in the 20th century.
Archeological research has revealed that there were two chapels located in this bailey, though only the foundations have been discovered. In the western bailey the ruins of a church, possibly dedicated to the Madonna, can still be seen along the wall. The rest of the buildings that once occupied this bailey have all been destroyed. In the north bailey there were certainly buildings, though they have been destroyed. The sheer cliff face was not fortified with a wall until the 14th or 15th century.
The Castles of Bellinzona are a group of fortifications located around the town of Bellinzona, the capital of the Swiss canton of Ticino. Situated on the Alpine foothills, the group is composed of fortified walls and three castles named Castelgrande, Montebello and Sasso Corbaro. The Castles of Bellinzona with their defensive walls have been an UNESCO World Heritage Site since 2000.
The Château Comtal (Count’s Castle) is a medieval castle within the Cité of Carcassonne, the largest city in Europe with its city walls still intact. The Château Comtal has a strong claim to be called a 'Cathar Castle'. When the Catholic Crusader army arrived in 1209 they first attacked Raymond-Roger Trencavel's castrum at Bèziers and then moved on to his main stronghold at Carcassonne.
The castle with rectangular shape is separated from the city by a deep ditch and defended by two barbicans. There are six towers curtain walls.
The castle was restored in 1853 by the architect Eugène Viollet-le-Duc. It was added to the UNESCO list of World Heritage Sites in 1997.